absorptivity

The quality of being absorptive; absorptiveness.

(thermodynamics) The fraction of radiation absorbed by a surface to the total radiation incident on the surface.

(analytical chemistry) The constant a in the Beer's law relation A = abc, where A is the absorbance, b the path length, and c the concentration of solution. Also known as absorptive power. Formerly known as absorbency index; absorption constant; extinction coefficient.